Wheel lifting apparatus

ABSTRACT

The invention is an electric powered mechanism for lifting and lowering at the wheels for an electric sweep type seismic vibrator source of the type used in seismic prospecting for hydrocarbons. The source uses an engine and generator combination to create electric power for all systems on the source such as driving a frame of linear electric motors that direct a rod or piston to contact the ground in a recurring fashion along with driving the source from location to location through a survey area. Preferably a foot is arranged on the bottom end of the rod or piston for contact with the ground and by engaging the grid of motors to push down against the ground in a rapid progression, acoustic energy is created and delivered into the ground for geophones to sense and record. The electric powered wheel mechanism may be utilized to bring the foot of the rod or piston in contact with the ground or in closer proximity to the ground or level the source prior to emitting the seismic energy or to adjust weight on the acoustic energy delivery system while seismic energy is being delivered.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims benefitunder 35 USC §119(e) to U.S. Provisional Application Ser. No. 61/640,349filed Apr. 30, 2012, entitled “WHEEL LIFTING APPARATUS,” which isincorporated herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

None.

FIELD OF THE INVENTION

This invention relates to vibratory seismic sources and particularly toseismic sources that are held to the ground to deliver vibratoryimpulses into the earth for seismic prospecting of hydrocarbons andother subsurface resources.

BACKGROUND OF THE INVENTION

In the process of acquiring seismic data, seismic energy is deliveredinto the earth. Over the years, the preferred attributes of the seismicenergy delivered into the earth have been honed to include a broadspectrum of wavelengths and sufficient power across the spectrum to berecorded at the surface. In general, a suitable land source must be ableto deliver seismic energy waves in a spectrum of wavelengths from about8 Hz up to 60-80 Hz. The source must have sufficient power across thespectrum so that the seismic waves have measurable amplitude at thesurface after transiting deep into the earth, reflecting from orrefracting through layers in the earth and transiting back to thesurface. A last major characteristic of a desirable seismic source isthat the energy from the source is distinguishable in the data recordfrom seismic energy from other sources whether from background sourcesor other seismic prospecting.

Explosive charges have long been used as seismic sources although theintense release of energy is typically not permitted except in remotelocations. Explosive sources, however, provide a wide array ofwavelengths with considerable power across the wavelengths.

Hydraulic reciprocating seismic vibrators or vibes have been in use formany years using a baseplate connected to hydraulic rams that cause areaction mass to reciprocate up and down to shake the ground through thebaseplate. The hydraulic rams are operated to move the reaction massthrough a sweep of the desired frequencies. However, the hydraulicsystems are limited in their ability to provide sufficient power at highfrequencies due to limitations of hydraulic flow in and out of thehydraulic cylinders. At very high hydraulic velocities, the hydraulicfluid is subject to cavitation when reversing directions that limits theamplitude of the movement of the reaction mass and thus the energy inputin to the earth. At low frequencies it is difficult for the hydraulicvibe to have enough travel to generate a low frequency wave into theground. For example, consider how one would generate a one Hz wave witha hydraulic vibe. A very long throw of the reaction mass is needed togenerate that wavelet because the mass has to be moving down and up thefull one second.

BRIEF SUMMARY OF THE DISCLOSURE

The invention more particularly relates to a vibratory seismic sourcefor delivering acoustic energy into the ground for seismic prospectingincluding a generator for creating electric power and a plurality oflinear motors arranged in a grid and each linear motor including a rodthat is arranged to move generally vertically to contact the ground witha lower end of the rod. A control system is included for controllingmovement of the rods such that the rods vibrate the ground and deliveracoustic energy into the ground. A plurality of wheels are included onwhich to convey the source from location to location wherein at leastone electrically powered motor is arranged to raise and lower the wheelsfor transiting around the survey area and adjust for delivering acousticenergy into the ground.

The invention also relates to process for delivering acoustic energyinto the earth for seismic prospecting where electric power is createdon a mobile seismic source and electric power is used on the mobileseismic to raise and lower wheels on the mobile seismic source andthereby raise and lower the seismic source with respect to the ground.The electric power is used to move a rod of a linear electric motorgenerally vertically to contact the ground with a lower end of the rodat the selected location and the movement of the rods is controlled suchthat the rods vibrate the ground and deliver acoustic energy into theearth.

“Generally vertical” or “generally vertically” should be interpreted asmeaning “with an axis of movement sufficiently nearly vertical withrespect to the ground so as effectively to impart energy to the ground.”Normally, the axis of movement would be less than 20 degrees tovertical, or in another embodiment less than 10 degrees to vertical.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and benefitsthereof may be acquired by referring to the follow description taken inconjunction with the accompanying drawings in which:

FIG. 1 is an elevation view of a discrete electric seismic source unit;

FIG. 2 is an enlarged fragmentary view of an electromechanical linearmotor assembly for delivering seismic energy into the ground;

FIG. 3 is an enlarged perspective fragmentary view of a grid of electromechanical linear motor assemblies for cooperatively delivering seismicenergy into the ground; and

FIG. 4 shows an enlarged fragmentary view of the mechanism for drivingand raising and lowering a wheel on the seismic source unit.

DETAILED DESCRIPTION

Turning now to the detailed description of the preferred arrangement orarrangements of the present invention, it should be understood that theinventive features and concepts may be manifested in other arrangementsand that the scope of the invention is not limited to the embodimentsdescribed or illustrated. The scope of the invention is intended only tobe limited by the scope of the claims that follow.

As shown in FIG. 1, an alternative vibrator seismic source 10 is showncomprising a chassis 12, four wheels 15 and a driver's cab 18. Thealternative vibrator actuator source 10 uses a diesel engine 21 to turnan electric generator 23 and uses electric power to power the source 10both for delivering acoustic energy into the ground and for moving alongthe ground from location to location. The source 10 utilizes electricityfor all of its power needs. An electric power accumulator 24, such as alarge battery, capacitor bank or both are included to store energy forhigh load situations of high electrical demand or when there areproblems with the generator 23, but the power accumulator 24 could alsoprovides the power to return to a location for repair.

Referring now to FIGS. 2 and 3, the acoustic energy delivery system 30is carried under the chassis 12 and comprises a frame 32 that carries anumber of linear motors 35. Linear motors are commercially availableequipment and each manufacturer has variations on the design, but inprincipal, each linear motor 35 includes a tubular body 36 and a rod oractuation bar 38 positioned within the tubular body 36 that extendstelescopically from the lower end of the tubular body 36. A replaceablefoot 39 is attached to the bottom end of the rod 38 for contacting theground. The frame 32 includes mounts for a grid of linear motors 35. Inone envisioned embodiment, the frame 32 has approximately 112 linearmotors 35 that are arranged in a grid of perhaps 8 by 14. Each linearmotor is capable of outputting a peak acceleration force ofapproximately 2400 Newtons (N) or approximately 540 pounds-force whileusing 34 amps RMS (Arms) at 240 volts AC. The 112 linear motors wouldthen be capable of outputting 268,800 N or 60,480 pounds-force usingapproximately 914 kilowatts of power. An additional advantage to thelinear motor is that they come in varying sizes and force output thatthat can be tuned to achieve a desired acceleration, force and sustainedvelocity of motion. Also, the electronic control for the linear motor iswell understood because of their wide use in manufacturing applications.

In operation, the frame 32 is lowered into proximity to the ground G andthe linear motors 35 are operated to lower the replaceable feet 39 intocontact with the ground G. Once all of the replaceable feet 39 are incontact with the ground G, the linear motors 35 are activated to thrustthe rods 38 toward the ground G and deflect the ground G and therebydeliver an impulse into the earth. The linear motors 35 are quicklyoperated to recoil the rods 38 under control without disengaging contactwith the ground G by the replaceable feet 39. By successive thrusts andrecoils, a sweep of acoustic energy is effectively delivered into theearth while the feet remain in contact with the ground G. It should benoted that the undulations and irregularities of the ground G may beaccommodated avoiding decoupling across the dimension of the frame 32.This method may be arranged to automatically compensate for surfacetopographic variations along with soft and hard spots on the groundsurface like rocks or logs. While it is recognized that ground typicallydoes not deflect much, it does not take much deflection with a 60,000pound vibrator holding the replaceable feet 39 to the ground G todeliver very useful acoustic energy. In this procedure, all of thelinear motors 35 would be operated at the same time using electricalpower created by the electric generator 23. The impulses would berepeated in a sequence where the impulse would occur with progressivelyincreasing or decreasing rapidity such that a progression of frequenciesof impulse forces would effectively deliver acoustic energy into theearth. The acoustic energy being characterizeable as a progressive sweepof frequencies covering a spectrum from about 1 Hz up to at least 80 Hzand preferably up to 120 Hz.

The electric linear motors 35, working in conjunction, would not sufferthe limitations of the hydraulic pumping systems at high frequency.Cycling electric power to the linear motors 35 to cause controlledmovement of the rods 38 within the tubular bodies 36 and with suchinstant response the impulse frequency range is greatly expanded. Byusing electrical control circuits that are commonly available for dieselelectric train locomotives and hybrid cars, the power can be appliedinstantly with a very high degree of control and stabilization. Linearmotors are highly controllable due to the ability to control the forceand velocity of the rods 38 via changes in the voltage and amperage ofthe applied current. Also the back-EMF generated can be accurately usedas a feedback circuit to compensate for variations in the wear patternsand ground impedance variations so that the combined sweep of the wholegroup of linear motors is consistent and repeatable.

It should be recognized that higher frequencies than typically deliveredmay be achievable by the source 10. Perhaps frequencies as high as 200Hz or higher may become useful in the field of seismic prospecting.There is no recognized reason that source 10 cannot deliver such highfrequency acoustic energy into the ground G. And it is generallyunderstood that high frequency energy provides high resolution data.Unfortunately, high frequency energy attenuates in the earth morerapidly than low frequency energy. With a large number of linearelectric motors, whether 2000, more than 2000 or less than 2000, will beable to deliver high energy at high frequency. The size of the linearmotors may be reduced or increased to adjust and adapt to ideal energydelivery system to create an optimal frequency range with high energyacross the spectrum. The selection of the specific linear motors is anengineering issue at production time because they can be sourced to havea large thrust force but with short strokes as compared to those thathave longer strokes with less thrust, but higher speeds. The alternativevibrator actuator source 10 invention is the substitution of electricpower for hydraulic power in a vibrator source. In a preferredembodiment the alternative vibrator actuator source 10 is comprised ofthe following main components: (1) a vehicle component comprising anarticulated vehicle chassis 12 with drivers' cab 18 capable ofsupporting the equipment and sustaining the rigors of a vibrator source;(2) a mechanical generator system that is made up of a diesel engine21-electric generator 23 package, an electric power accumulator 24,power conditioner, power distribution center, and all necessary cablesand switches; (3) an electromechanical acoustic energy delivery system30; and (4) a control system for controlling the delivery of acousticenergy by the electromechanical acoustic energy delivery system 30.

In the preferred embodiment of the present invention, the seismic source10 utilizes electric motors at each wheel 15 to drive the source 10around the survey area similar to what is used in other electricpropelled trucks, hybrid cars or even golf carts. Turning now to FIG. 4,the wheels are mounted to the chassis 12 of the source 10 using agrooved yoke 41 and a block 42. The yoke 41 is fixed to the chassis 12by bolts or welding and the block is arranged to move or slidevertically within the yoke to raise and lower the wheel. Motor 43 ismounted within the block 42 which attaches directly to the wheel andcauses the wheel 15 to rotate to propel the source 10. The block 42 israised and lowered by interaction of a screw rod 51 attached to theblock 42 and a screw drive 53. An electric stepper motor 54 is attachedto the screw drive 53 to raise and lower the screw rod 51 and therebyraise and lower the block 42. A load sensor 52 is arranged at theconnection of the screw rod 51 and the block 42 to sense the weight ofthe source on the wheel 15. A motion sensor 55 senses vertical movementat the wheel. Both sensors 52 and 55 report their information to acentral control system (not shown) on the source 10. In operation, thesource 10 may move onto a predetermined source location and either lowerthe frame 32 to put the linear motors 35 into proximity with the ground.Alternatively, the source may squat down to bring the frame 32 intoproximity with the ground by raising the wheels using the screw rod 51.Secondly, the wheels 15 may be individually adjusted to provide thesource 10 into a more level or horizontal orientation. Third, one aspectof providing effect acoustic energy into the earth is to have asignificant portion of the weight of the source 10 be applied to theground through the rods 38 and for the weight to be as consistent aspossible through the sweep of the impulses. Load sensor 52 is arrangedto measure the amount of weight being born by the respective wheel 15and the step motor 54 may adjust the height of the wheel 15 through thescrew rod 51 to maintain consistent weight on the wheel, and effectivelymaintain a consistent weight on the rods 38.

In closing, it should be noted that the discussion of any reference isnot an admission that it is prior art to the present invention,especially any reference that may have a publication date after thepriority date of this application. At the same time, each and everyclaim below is hereby incorporated into this detailed description orspecification as a additional embodiments of the present invention.

Although the systems and processes described herein have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made without departing from the spirit and scopeof the invention as defined by the following claims. Those skilled inthe art may be able to study the preferred embodiments and identifyother ways to practice the invention that are not exactly as describedherein. It is the intent of the inventors that variations andequivalents of the invention are within the scope of the claims whilethe description, abstract and drawings are not to be used to limit thescope of the invention. The invention is specifically intended to be asbroad as the claims below and their equivalents.

1. A vibratory seismic source for delivering acoustic energy into theground for seismic prospecting, the source comprising: a) a generatorfor creating electric power; b) a plurality of linear motors arranged ina grid and each including a rod that is arranged to move generallyvertically to contact the ground with a lower end of the rod; c) acontrol system for controlling movement of the rods such that the rodsvibrate the ground and deliver acoustic energy into the ground; and d) aplurality of wheels on which to convey the source from location tolocation; and e) at least one electrically powered motor to raise andlower the wheels for transiting around the survey area and adjust fordelivering acoustic energy into the ground.
 2. The vibratory seismicsource according to claim 1, wherein the linear motors are carried by aframe, and the source includes an electric powered system to raise andlower the frame to the ground so that the rods may be operated intocontact with the ground and raised up and clear of the ground when thesource is moved from location to location.
 3. The vibratory seismicsource according to claim 1, further including a diesel engine to drivethe generator.
 4. The vibratory seismic source according to claim 1,wherein the mobile seismic source includes at least three wheels andeach wheel includes a screw rod and screw drive assembly to individuallyraise and lower each of the three wheels on the mobile seismic source.5. The vibratory seismic source according to claim 4, wherein the screwrod and screw drive assembly for each wheel further includes a loadsensor to sense the weight on each wheel so that the effective weight onthe ground through the lower ends of the rods may be monitored, adjustedor maintained while acoustic energy is delivered into the earth.
 6. Thevibratory seismic source according to claim 1, wherein the linear motorsare arranged in a grid between 10 and 5,000, such as between 100 and2,000, for example between 200 and 1,000.
 7. A process for deliveringacoustic energy into the earth for seismic prospecting, the processcomprising: a) creating electric power on a mobile seismic source; b)using electric power on the mobile seismic to raise and lower wheels onthe mobile seismic source and thereby raise and lower the seismic sourcewith respect to the ground; c) using the electric power to move a rod ofa linear electric motor generally vertically to contact the ground witha lower end of the rod at the selected location; and d) controllingmovement of the rods such that the rods vibrate the ground and deliveracoustic energy into the earth.
 8. The process for delivering acousticenergy into the earth according to claim 6 further including the step oflowering each of the rods to the ground and maintaining the lower endsof the rods in continuous contact with the ground as the acoustic energyis delivered into the earth.
 9. The process for delivering acousticenergy into the earth according to claim 7 wherein the rods aresuccessively thrust against the ground and recoiled away from the groundwithout losing contact with the ground to deliver a series of impulsesinto the earth such that the timing for the impact, recoiling andsuccessive impact progresses through a frequency spectrum to include arange of frequencies for acquiring reflections from the earth atgeophones arrayed across a survey area.
 10. The process for deliveringacoustic energy into the earth according to claim 7 wherein the step ofraising a lowering the wheels is performed to maintain a consistentweight of the vibe through the lower ends of the rods and onto theground while delivering acoustic energy into the earth.
 11. The processfor delivering acoustic energy into the earth according to claim 7wherein the step of raising a lowering the wheels is performed tomaintain the mobile seismic source relatively level while deliveringacoustic energy into the earth.
 12. The process for delivering acousticenergy into the earth according to claim 7 wherein the step of raising alowering the wheels is performed to lower the mobile seismic source sothat the rods are in close proximity to the ground prior to lowering therods to the ground.
 13. The process for delivering acoustic energy intothe earth according to claim 6 wherein a plurality of rods, e.g. between10 and 5,000, such as between 100 and 2,000, for example between 200 and1,000.